I couldn't find anywhere to buy it other than sourdo.com - and they charge a fortune for shipping. I ended up buying some while I was in Florida on holiday last year. I tarries dried and is a bit of a pain to activate.
If you like, I could put some live Ischia culture in the mail to you - it shouldn't take more than a couple of days from UK to Germany so it should arrive alive just fine. Especially as it's winter now. No charge other than covering postage.
PM me if you are interested.